Method and apparatus for image filtering

ABSTRACT

A system that incorporates the subject disclosure may include, for example, partitioning the image into a group of blocks, calculating principle bilateral filtered image components for a first subset of the group of blocks where the principle bilateral filtered image components are not calculated for a second subset of the group of blocks, and applying an infinite impulse response filter to the image using the principle bilateral filtered image components. Other embodiments are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of and claims priority to U.S. patentapplication Ser. No. 14/031,188 filed Sep. 19, 2013, the disclosure ofwhich is hereby incorporated by reference into this application as ifset forth herein in full.

FIELD OF THE DISCLOSURE

The subject disclosure relates to a method and apparatus for imagefiltering.

BACKGROUND

Media services that include transmitting images are in high demand.Consumers desire quality images but also desire little delay inreceiving the images. To meet these demands, filtering methods have beenimplemented. These filtering methods can require a large amount ofcomputational resources to achieve a desired level of filteringaccuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale, and wherein:

FIG. 1 depicts an illustrative embodiment of a Gaussian filter and itstruncated version;

FIG. 2 depicts an illustrative embodiment of a coherent region for aforward vertical pass during bilateral filtering;

FIG. 3 depicts an illustrative embodiment of a portion of an image thathas been partitioned into blocks where a pixel (the black dot) has anintensity in the range (L_(i−1), L_(i+1)), and where the PBFIC(L_(i))can be computed for all the shaded area covering nine blocks.

FIG. 4 depicts processing speed improvements according to the exemplaryembodiments;

FIG. 5 depicts an illustrative method for performing image filteringbased on partitioning of an image;

FIG. 6 depicts an illustrative embodiment of a communication system thatprovides media services including image filtering;

FIG. 7 depicts an illustrative embodiment of a communication device; and

FIG. 8 is a diagrammatic representation of a machine in the form of acomputer system within which a set of instructions, when executed, maycause the machine to perform any one or more of the methods describedherein.

DETAILED DESCRIPTION

The subject disclosure describes, among other things, illustrativeembodiments of image filtering. One or more of the exemplary embodimentsutilize bilateral filtering that is selectively applied to blocks of animage to perform image filtering. For example, Yang's realtime O(1)bilateral filtering algorithm (see Q. Yang, K.-H. Tan, and N. Ahuja,“Real-time O(1) bilateral filtering,” in Proc. CVPR '09, pp. 557-564,2009, the disclosure of which is hereby incorporated herein by referencein its entirety) can be accelerated or otherwise facilitated based onstrategically eliminating some of the computation. To identifycomputation for elimination from the algorithm, the algorithm steps canbe analyzed in conjunction with its recursive Gaussian filteringcomponent. By block partitioning the image, the procedure to isolate thecomputation steps to be eliminated is simplified, and the modifiedalgorithm skips some of the image blocks when performing recursivelinear filtering. In one or more embodiments, the resultant acceleratedalgorithm is able to achieve 1.5 to 5 times speedup, depending on theimage statistics and the filtering parameters. The exemplary embodimentmay marginally degrade the accuracy of the filtering, but the simplicityand small memory footprint of Yang's original algorithm are largelymaintained. Other embodiments are included in the subject disclosure.

One embodiment of the subject disclosure is a method that includesaccessing an image and partitioning the image into a group of blocksincluding first blocks, first surrounding blocks that are each adjacentto one of the first blocks, second blocks, and second surrounding blocksthat are each adjacent to one of the second blocks. The method caninclude calculating principle bilateral filtered image components forthe first blocks responsive to determinations that a first pixel withineach of the first blocks has a first intensity level within apre-determined intensity range or responsive to a determination that asecond pixel within the first surrounding blocks has a second intensitylevel within the pre-determined intensity range. The principle bilateralfiltered image components are not calculated for the second blocksresponsive to a determination that pixels within the second blocks haveintensity levels outside of the pre-determined intensity range andresponsive to a determination that pixels within the second surroundingblocks have intensity levels outside of the pre-determined intensityrange. The method can include applying an infinite impulse responsefilter to the image using the principle bilateral filtered imagecomponents.

One embodiment of the subject disclosure includes a computer-readablestorage device comprising computer instructions which, responsive tobeing executed by a processor, cause the processor to perform operationscomprising accessing an image and partitioning the image into a group ofblocks. The processor can calculate principle bilateral filtered imagecomponents for a first subset of the group of blocks, where theprinciple bilateral filtered image components are not calculated for asecond subset of the group of blocks. The processor can apply aninfinite impulse response filter to the image using the principlebilateral filtered image components.

One embodiment of the subject disclosure includes a device having amemory to store computer instructions, and a processor coupled with thememory. The processor, responsive to executing the computerinstructions, can perform operations including accessing an image andpartitioning the image into a group of blocks. The processor cancalculate principle bilateral filtered image components for a firstsubset of the group of blocks, where the principle bilateral filteredimage components are not calculated for a second subset of the group ofblocks. The processor can apply an infinite impulse response filter tothe image using the principle bilateral filtered image components.

One or more of the exemplary embodiments can utilize a form of bilateralfiltering as an edge preserving smoothing filter. Unlike a Gaussianfilter which smoothes the image in a spatially invariant manner, thebilateral filter has a factor which can control the smoothing using theintensity (color) domain information. This added control can enable thebilateral filtering to effectively preserve the strong edges whilesmoothing away the undesirable noises, leading to many applications suchas image de-noising, tone mapping, flash/no-flash fusion and/or stereomatching. The benefit of edge preserving smoothing via the exemplaryembodiments is not without its computational cost. The bilateral filteris essentially a non-linear filter, and can be computationallyexpensive.

Among the fastest existing bilateral filtering algorithms is Yang'sreal-time O(1) bilateral filtering algorithm, where O(1) refers to aconstant factor of computation per image pixel. This algorithm generatesthe filtered image by first computing the Principle Bilateral FilteredImage Component (PBFIC) through recursively linearly filtering twointermediate images, then linearly interpolating between two adjacentPBFICs. The main step in computing the PBFICs is spatial invariantlinear filtering, which is understood and less expensive computationallythan non-linear filtering. This algorithm is able to produce veryaccurate bilateral filtered result with a small memory footprint. In theexemplary embodiments, Yang's algorithm can be enhanced, based on theobservation that in Yang's original algorithm some of the computationsfor the PBFICs are wasteful. To reduce such wasteful computations, thecomputation steps are analyzed in conjunction with the recursiveGaussian filtering procedure to isolate them, and skip some of the imageblocks to avoid a large portion of such computation. The resultantprocess of the exemplary embodiments is able to achieve at least 1.5 to5 times speed up, depending on the image statistics and the filteringparameters.

Mathematically, the bilateral filtering operation performs the followingcomputation for each pixel x in an image:

$\begin{matrix}{{{I^{B}( \overset{->}{x} )} = \frac{\Sigma_{\overset{->}{y} \in {N{(\overset{\_}{x})}}}{{f_{S}( {\overset{->}{x},\overset{->}{y}} )} \cdot {f_{R}( {{I( \overset{->}{x} )},{I( \overset{->}{y} )}} )} \cdot {I( \overset{->}{y} )}}}{\Sigma_{\overset{->}{y} \in {N{(\overset{\_}{x})}}}{{f_{S}( {\overset{->}{x},\overset{->}{y}} )} \cdot {f_{R}( {{I( \overset{->}{x} )},{I( \overset{->}{y} )}} )}}}},} & (1)\end{matrix}$

where I(x) is the intensity value at pixel location x, N(x) is aspecific neighborhood of x, f_(S)(x, y) is the spatial filtering kerneldepending only on the pixel locations x and y, and f_(R)(I(x), I(y)) isthe range filtering kernel depending only on the intensity I(x) andI(y). The original bilateral filtering uses Gaussian-like filter ofdifferent variances for the spatial filtering kernel f_(S)(x, y) andrange filtering kernel f_(R)(I(x), I(y)),

f _(S)({right arrow over (x)},{right arrow over (y)})=exp(−∥{right arrowover (x)}−{right arrow over (y)}∥ ²/2σ_(S) ²).  (2)

f _(S)(I({right arrow over (x)}),I({right arrow over(y)})=exp(−(I({right arrow over (x)})−I({right arrow over (y)}))²/2σ_(R)²).  (3)

where σ_(S) and σ_(R) are the spatial kernel variance and the rangekernel variance, respectively. The kernel functions f_(S)(x, y) andf_(R)(I(x), I(y)) have since been generalized to other filters, e.g., tothe box-filter spatial kernel.

Yang's real-time O(1) bilateral filtering algorithm can be described asfollows. For a digital image, there are only a finite number of possibleintensity values, i.e., I(x)ε{0, 1, . . . N−1}. For each intensityvalue, kε{0, 1, . . . N−1} in a given image, the following twoquantities are only functions of the pixel location y

W _(k)

f _(R)(k,I({right arrow over (y)})), J _(k)

W _(k)({right arrow over (y)})·I({right arrow over (y)}),  (4)

Now (1) can be written as

I ^(B)({right arrow over (x)})=I _(l({right arrow over (x)}))^(B)({right arrow over (x)}),  (5)

where by denoting I(x)=k

$\begin{matrix}{{I_{k}^{B}( \overset{->}{x} )}\overset{\bigtriangleup}{=}{\frac{J_{k}^{\prime}( \overset{->}{x} )}{W_{k}^{\prime}( \overset{->}{x} )} = {\frac{\Sigma_{\overset{->}{y} \in {N{(\overset{->}{x})}}}{{f_{S}( {\overset{->}{x},\overset{->}{y}} )} \cdot {J_{k}( \overset{->}{y} )}}}{\Sigma_{\overset{->}{y} \in {N{(\overset{->}{x})}}}{{f_{S}( {\overset{->}{x},\overset{->}{y}} )} \cdot {W_{k}( \overset{->}{y} )}}}.}}} & (6)\end{matrix}$

Both the numerator and the denominator in (6) are spatial-invariantlinear Gaussian filtering, which can be computed efficiently using arecursive method such as described in R. Deriche, “Fast algorithms forlow-level vision,” IEEE Trans. PAMI, vol. 12, no. 1, pp. 78-87, 1990 andR. Deriche, “Recursively implementing the Gaussian and its derivatives,”Tech. Rep. 1893 INRIA, Unit de Recherche Sophia-Antipolis, 1993, thedisclosures of which are hereby incorporated by reference in theirentirety.

This gives the bilateral filtered value for pixels of intensity k. Bysweeping through all possible intensities, the bilateral filtered valuefor each pixel can be determined. Each of these I^(B) _(k)(x) images iscalled a Principle Bilateral Filtered Image Component (PBFIC). Yang'sreal-time O(1) bilateral filtering algorithm is built on the observationthat there is no need to compute PBFIC for all the intensity levels, butinstead only PBFICs for K<N levels (denoted as {L₀,L₁, . . . , L_(K-1)}where L₀ and L_(K-1) are the lower and upper limits of the dynamicrange, respectively) need to be computed; for notational simplicity,they can be written as PBFIC(L₀), PBFIC(L₁), . . . , PBFIC(L_(K-1)). Thefinal bilateral filtered value I^(B)(x) at location x can then belinearly interpolated using the values at location x of PBFIC(L_(i-1))and PBFIC(L_(i)) for any pixel x such that I(x)ε(L_(i-1), L_(i)), i.e.,using the linear combination of them with respective weights:

$\frac{L_{i} - {I( \overset{->}{x} )}}{L_{i} - L_{i - 1}}\mspace{20mu} \frac{{I( \overset{->}{x} )} - L_{i - 1}}{L_{i} - L_{i - 1}}$

An advantage of this algorithm is its small memory footprint, becauseone could sweep through {L₀, L₁, . . . . ,L_(K-1)}, and only twoadjacent PBFICs need to be kept such that for any pixels whoseintensities fall into this range, their filtered values can be correctlyobtained. Since the Gaussian filter is separable, the overall processcan be decomposed into horizontal and vertical filtering. The onedimensional recursive algorithm of Deriche (referenced above) includes aforward pass and a backward pass, each one of which is a linearfiltering using an infinite impulse response (IIR) filter, and thecombination of these two passes leads to an accurate approximation ofthe Gaussian smoothing.

As an example, consider the case where the image pixel intensity valuesare all in the range of (L₀, L₁). When Yang's algorithm is used on thisimage, since the filtered result I^(B)(x) at each pixel is completelydetermined by PBFIC(L₀) and PBFIC(L₁), the other PBFICs are useless, andthus computing them is unnecessary and wasteful. This simple observationis the main motivation for the improvement proposed in this work. Thisextreme case example may leave the impression that for a given pixel x,we only need to compute the two levels of PBFICs at those locations xwhere I(x) is sandwiched in between. This is however not the case whenthe recursive filtering method is used. For simplicity, let us considerthe one-dimensional case, and assume the IIR filter is given as

y[n]=a ₀ x[n]+a ₁ x[n−1]+b ₁ y[n−1]−b ₂ y[n−2],  (7)

where x[n] is the input at location n, and y[n] is the filtered outputat location n. Because the recursive IIR filter relies on the(previously computed) causal filtering result when computing the currentoutput, in order to compute y[n₀], all y[m]'s for m<n₀ essentially needto be computed. This suggests that as long as a single pixel in theimage has an intensity in the range [L_(i-1), L_(i)), then the wholeimage-sized PBFIC(L_(i)) and PBFIC(L_(i-1)) (or at least some “causalportion” of them) will need to be computed. This may not lead tosignificant savings in computation. Note however that since the Gaussianfilter has a rather short (fast decaying) tail, it can be truncatedaggressively in practice as shown in FIG. 1. When the Gaussian filteringis computed using the recursive method, this is equivalent to sayingthat faraway signals can be ignored completely. More precisely, whencomputing the filtered output of (7) at location no using a truncatedversion of the signal x[n], i.e., using x′[n]=0 for n<n_(o)−c, andx′[n]=x[n] for n>=n_(o)−c, the difference from the true filtered valueusing x[n] is very small when c is sufficiently large. In practice, amoderate value of c is usually sufficient and can be denoted as c_(o)and called the coherent width. The precise choice of c_(o) can beapplication dependent. With the coherent width c_(o) fixed, the previousmentioned difficulty is alleviated. To compute y[n₀] within a smallerror, only additional y[m]'s for m=n_(o)−c_(o), n₀−c_(o+1), . . . n₀₋₁need to be computed. For two-dimensional filtering on an image, theconcept of the coherent length can be generalized to the concept of thecoherent region. For example, for the forward vertical filter pass, thecoherent region is illustrated in FIG. 2. Combining it with the coherentregion of the backward vertical filter pass, as well as the forward andbackward horizontal filter passes, the overall coherent region is asquare neighborhood of size (2c_(o)+1)×(2c_(o)+1) with the pixel at thecenter. This implies if the intensity value of a pixel x_(o) issandwiched between two levels L_(i) and L_(o+1), then we only need tocompute J′_(Li)(x), W′(x), J′_(Li+1)(x) and W′_(Li+1)(x) for x in asquare neighborhood of size (2c_(o+1))×(2c_(o+1)) with x_(o) at thecenter. Note that we could potentially distinguish the differentcoherent regions for the four filter passes, but this may complicate thealgorithm.

Following the above discussion, we could generate computation maps for agiven image for the specified levels L₀, L₁, . . . L_(K-1) using amorphological dilation operation, and avoid all unnecessary computationsfollowing these maps. This naive approach may be counter-productivesince directly computing such maps is relatively (to Yang's originalalgorithm) expensive, defeating the purpose of accelerating thealgorithm. However, the exemplary embodiments can provide an approach toapproximate such maps.

The first simplification is to partition the image into blocks of sizec_(o)×c_(o), and thus instead of considering whether PBFIC(L_(k)) needsto be computed for a given pixel in the image, we consider whether itneeds to be computed for a given block B(p, q), where p and q are itshorizontal and vertical indices. Following the discussion above, it isclear that PBFIC(L_(i)) should be computed for block B(p, q) if

-   -   there exists a pixel, whose intensity value is in the range        (L_(i-1), L_(i+1)), in B(p, q), or    -   there exists a pixel, whose intensity value is in the range        (L_(i-1), L_(i+1)), in the eight neighboring blocks of B(p, q).

The first case is necessary because of the filter computation for thatparticular pixel, and the second case is because the pixel in B(p, q)may be in the coherent region of a certain pixel of interest in theneighboring blocks, as illustrated in FIG. 3. In a given image blockB(p, q), the maximum pixel intensity value and the minimum pixelintensity value can be denoted as max(p, q) and min(p, q), respectively.To determine whether there exists a pixel in B(p, q) in the range(L_(i-1), L_(i+1)) such that PBFIC(L_(i)) needs to be computed for thisblock, a simplification can be made to assume there is such a pixelunless:

L _(i-1)≧max(p,q) or L _(i+1)<min(p,q),  (8)

That is, an assumption can be made that the pixels in block B(p, q) takeup all the intensity values between max(p, q) and min(p, q). Althoughthis is in general may not always be true, it does not make significantdifference in practice, and leads to a simpler algorithm.

One or more of the exemplary embodiments can have a pre-filtering stageto find the maximum and minimum values of a block, moreover to find foreach block the maximum and minimum values in the region consisting ofits own and its neighboring blocks. For example, the pre-filtering Step:

1) For each block B(p, q), find max(p, q) and min(p, q);2) For each block B(p, q), find max′(p, q) and min′(p, q) where

${\max^{\prime}( {p,q} )}\overset{\bigtriangleup}{=}{\max\limits_{{{{i - p}} \leq 1},{{{j - q}} \leq 1}}{\max ( {i,j} )}}$${\min^{\prime}( {p,q} )}\overset{\bigtriangleup}{=}{\min\limits_{{{{i - p}} \leq 1},{{{j - q}} \leq 1}}{{\min ( {i,j} )}.}}$

For simplicity, we have implicitly assumed above that (i, j) is onlyenumerated for blocks that exists in the image. The other part of theprocess can utilize portions of Yang's original algorithm, except whenperforming the recursive filtering. To be more precise, consider thehorizontal forward filtering pass to compute Fu (x) for a given row,which lies within the row of blocks B(p, 1), B(p, 2), . . . B(p, m);recall the block is of size c_(o)×c_(o), then

Horizontal Pass for a Row of pixels: For q=1, 2, . . . m

-   -   1) If L_(i-1)<max′(p,q) and L_(i+1)≧min′(p,q)        -   a). If B(p,q−1) was not filtered, initialize the IIR filter;        -   b): Filter the row segment within the block B(p,q) using the            IIR titter;

The precise initialization settings can be found in the Derichereferences describes above, but of importance is the fact that it onlydepends on the pixels intensity at the boundary of the current block.Note that the block B(p, −1) clearly does not exist, and thus in theabove algorithm it would be considered as not filtered. The above rowfiltering procedure is done on each row of the image J_(Li) and W_(Li).The other three passes are done similarly, which eventually give J′_(Li)and W′_(Li), and subsequently PBFIC(L_(i)).

Another benefit of using the block structure is in updating theresultant filtered image I^(B)(x). In the original algorithm, whenPBFIC(L_(i)) and PBFIC(L_(i+1)) have been computed, the image is thenscanned for any pixel whose intensity falls between these two levels,and the filtered values are updated for these locations using linearinterpolation. However, since we have recorded max(p, q) and min(p, q),if max(p, q)<L_(i) or min(p, q)≧L_(i+1), there is no need to search forsuch pixels within B(p, q). This provides some noticeable but lesssignificant speedup, because the most expensive computation is incomputing PBFICs, but not in these updating steps.

Example

We evaluated the performance of the proposed process using asingle-thread C/C++ implementation. The computer used had 2G memory anda 3.33 GHz Intel i7-980X processor on Windows 7 platform. Theimplementation utilized the OpenCV library, and to eliminate any unfairadvantage we implemented Yang's original algorithm using this library.The parameters σ_(S) and σ_(R) are application dependent, however, theycan be selected in the range 4 to 40 and 0.04 to 0.3, respectively, asan example. The higher the number of levels K, the better the filteringaccuracy at the cost of more computation; it can be sufficient to use Kin 4 to 25 range when the dynamic range is 0 to 255 depending on theaccuracy requirement of the applications (usually 40 dB is consideredsufficient). Empirically, we found that choosing c_(o)=σ_(S) offers agood tradeoff between accuracy and efficiency for the typical range ofσ_(S) and σ_(R) given above, and it is used for the example; for largeσ_(S) values, the advantage of the proposed technique diminishes (seeFIG. 4), and by setting c_(o) larger, the exemplary process reduces tothe efficiencies of Yang's original algorithm.

In this example, thirty randomly chosen images (from the Internet) wereused, the content of which included people, natural sceneries,buildings, plants and animals; where the images had sizes in the range0.5 to 6 million pixels. The naïve implementation of the bilateralfiltering was used to compute the ground-truth. We first compared theaccuracy of the exemplary process and the reference algorithm (each tothe ground-truth). The measure used is the relative difference in peaksignal-to-noise ratio (PSNR) defined as:

${{rd}\text{-}P\; S\; N\; R} = {\frac{{P\; S\; N\; {R_{ref}( {K,\sigma_{S},\sigma_{R}} )}} - {P\; S\; N\; {R_{pro}( {K,\sigma_{S},\sigma_{R}} )}}}{P\; S\; N\; {R_{ref}( {K,\sigma_{S},\sigma_{R}} )}}.}$

where PSNR_(ref) (K, σ_(S), σ_(R)) and PSNR_(pro) (K, σ_(S), σ_(R)) arethe PSNRs of the filtered results by the reference algorithm and that bythe exemplary process, respectively, with parameters (K, σ_(S), σ_(R))for a given image. The parameters σ_(S) is sampled as in FIG. 4, σ_(R)is sampled at (0.04, 0.06, 0.08, 0.1, 0.12, 0.15, 0.18, 0.25, 0.3), andK is sampled at (4, 6, 8, 10, 12, 15, 25). The average (over the testimages and the sampled parameters) rd-PSNR is 0.0115 and the variance is5.97×10⁻⁴. The inaccuracy increases as σ_(R) and σ_(S) increase, withits dependence on σ_(S) being more prominent; the rd-PSNR is almost 3%at large σ_(R) and σ_(S) when averaged over the test images, while beingless than 1% at the other extreme. We deem this kind of accuracydegradation acceptable because at the targeted quality (PSNR 40-55 dB),less than 1 dB difference is usually negligible for typical applicationsof the bilateral filter. One can improve the accuracy by choosing a moreconservative c_(o) at the cost of a reduced speedup. Next we considerthe speedup of the proposed method. From the structure of the method, itis clear that the speedup does not depend on the parameter σ_(R)critically, and thus we plot the average speedup (over the test imagesand σ_(R)) vs σ_(S) for fixed K values in FIG. 4. It can be seen thatthe smaller the value σ_(S), the more effective the proposed method is.This is because c_(o)=σ_(S) and smaller c_(o) allows the method toeliminate the unnecessary computations more effectively. The method isalso more effective for larger values of K because this usually impliesa larger proportion of the PBFIC computations in the original algorithmare unnecessary, which provides the proposed method a larger target toreduce. As an example, on a typical 1.5 mega-pixel image, the exemplaryprocess is able to complete in 383 ms with parameters σ_(R)=0.06 andσ_(S)=15, while Yang's original algorithm completes in 835 ms with 45 dBaccuracy.

One or more of the exemplary embodiments can accelerate Yang's bilateralfiltering algorithm by eliminating unnecessary computations throughblock-skipping IIR filtering. The modified process can achieve speedupof 1.5 to 5 times. Although only Gaussian kernels are described herein,the example methods can be applied to other IIR spatial filteringkernels with a short tail (e.g., the box filter). Further, downsamplingof the image can also be utilized to further speed up the process. Theexample method can also be used in a GPU-based implementation, toachieve a speed up in the range of 1.1 to 1.3 in a CUDA-basedimplementation. To take advantage of the parallelism in the GPU, wechoose c_(o) to be a multiple of 16 or 32.

FIG. 5 depicts an illustrative method 500 for performing imagefiltering. Method 500 enables a more computationally efficient bilateralfiltering process, such as based on adjustments to Yang's real-timebilateral filtering algorithm. Method 500 can block partition an image,and skip some of the blocks so that unnecessary computations are avoidedduring the recursive linear filtering. The resultant accelerated processof method 500 is able to achieve improved processing time (e.g., 1.5-5times speedup).

Method 500 can begin at 502 where an image is accessed or otherwiseobtained. The image can be of various sizes, such as from 0.5 millionpixels to 6 million pixels, although the method 500 can be applied toimages having less pixels or more pixels than this described range. Theimage can be obtained by and the method 500 can be implemented byvarious devices or combinations of devices, such as a set top box,desktop computer, mobile communication device, server, and so forth.Method 500 is described with respect to an image, but it should beunderstood that the methodology described herein can be applied to anynumber of images, which can be still images or video content.

At 504, the image can be partitioned or otherwise defined into a groupof blocks. In one embodiment, the blocks can be of the same size. Inanother embodiment, the blocks can be square blocks. The size of theblocks can vary based on a number of factors, such as the total numberof pixels for the image, the desired filtering computation time, thecapabilities of the device performing method 500, the desired accuracyfor the filtering, and so forth. In one embodiment, each block of thegroup of blocks can have a size of c_(o) by c_(o), where c_(o) is equalto a spatial kernel variance utilized by an infinite impulse responsefilter (described with respect to step 506).

At 506, PBFICs can be selectively computed for certain blocks withoutbeing computed for other blocks of the group of blocks. As an example,the group of blocks can include first blocks, first surrounding blocksthat are each adjacent to one of the first blocks, second blocks, andsecond surrounding blocks that are each adjacent to one of the secondblocks. PBFICs can be calculated for the first blocks responsive todeterminations that a first pixel within each of the first blocks has afirst intensity level within a pre-determined intensity range orresponsive to a determination that a second pixel within the firstsurrounding blocks has a second intensity level within thepre-determined intensity range. Continuing with this example, method 500can save computational resources by not calculating PBFICs for thesecond blocks where there is a determination that pixels within thesecond blocks have intensity levels outside of the pre-determinedintensity range and responsive to a determination that pixels within thesecond surrounding blocks have intensity levels outside of thepre-determined intensity range. The exemplary method can utilize aninfinite impulse response filter applied to the image using calculatedprinciple bilateral filtered image components for selective blocks ofthe image.

Upon reviewing the aforementioned embodiments, it would be evident to anartisan with ordinary skill in the art that said embodiments can bemodified, reduced, or enhanced without departing from the scope of theclaims described below. For example, pre-filtering can be performed onthe image to facilitate the selective calculation of PBFICs forselective blocks. For instance, the pre-filtering can includedetermining a maximum intensity and a minimum intensity for each blockof the group of blocks. The pre-filtering can be performed by the samedevice performing the filtering or can be performed by another device.As an example, a sending device that is forwarding the image to arecipient device can perform pre-filtering of the image and can providethe results of the pre-filtering with the image (such as in metadata) tothe recipient device, so that the recipient device can perform the PBFICcalculations and IIR filtering on the image. This example provides adistributed implementation of method 500 between the sending device andthe recipient device which can further improve the image processingbeing performed by the recipient device.

In another embodiment, downsampling of the image can be performed whichcan further facilitate the image processing by the recipient device. Inanother embodiment, a GPU can be used to perform all or a portion ofmethod 500. For example, each block of the group of blocks can have asize of c_(o) by c_(o), where c_(o) is selected to be a multiple of 16to facilitate processing by the GPU.

Other embodiments can be used in the subject disclosure.

It should be understood that devices described in the exemplaryembodiments can be in communication with each other via various wirelessand/or wired methodologies. The methodologies can be links that aredescribed as coupled, connected and so forth, which can includeunidirectional and/or bidirectional communication over wireless pathsand/or wired paths that utilize one or more of various protocols ormethodologies, where the coupling and/or connection can be direct (e.g.,no intervening processing device) and/or indirect (e.g., an intermediaryprocessing device such as a router).

FIG. 6 depicts an illustrative embodiment of a communication system 600for delivering media content. The communication system 600 can representan Internet Protocol Television (IPTV) media system. Communicationsystem 600 enables image processing that saves computational resources.For example, one or more devices in system 600 can access an image andpartition the image into a group of blocks. The one or more device canthen selectively calculate PBFICs for a first subset of the group ofblocks, while not calculating PBFICs for a second subset of the group ofblocks. Infinite impulse response filtering can be applied to the imageby the one or more devices using the selectively calculated PBFICs. Aselection of the first subset of the group of blocks can be based ondeterminations that a first pixel within each block of the first subsethas a first intensity level within a pre-determined intensity range orresponsive to a determination that a second pixel within a surroundingblock of each block of the first subset has a second intensity levelwithin the pre-determined intensity range. The PBFICs may not becalculated for the second subset of the group of blocks responsive to adetermination that pixels within the second subset have intensity levelsoutside of a pre-determined intensity range and responsive to adetermination that pixels within surrounding blocks of the second subsethave intensity levels outside of the pre-determined intensity range. Byonly calculating PBFICs for certain blocks, computational resources ofthe one or more devices can be saved without a significant reduction inimage accuracy.

The IPTV media system 600 can include a super head-end office (SHO) 610with at least one super headend office server (SHS) 611 which receivesmedia content from satellite and/or terrestrial communication systems.In the present context, media content can represent, for example, audiocontent, moving image content such as 2D or 3D videos, video games,virtual reality content, still image content, and combinations thereof.The SHS server 611 can forward packets associated with the media contentto one or more video head-end servers (VHS) 614 via a network of videohead-end offices (VHO) 612 according to a multicast communicationprotocol.

The VHS 614 can distribute multimedia broadcast content via an accessnetwork 618 to commercial and/or residential buildings 602 housing agateway 604 (such as a residential or commercial gateway). The accessnetwork 618 can represent a group of digital subscriber line accessmultiplexers (DSLAMs) located in a central office or a service areainterface that provide broadband services over fiber optical links orcopper twisted pairs 619 to buildings 602. The gateway 604 can usecommunication technology to distribute broadcast signals to mediaprocessors 606 such as Set-Top Boxes (STBs) which in turn presentbroadcast channels to media devices 608 such as computers or televisionsets managed in some instances by a media controller 607 (such as aninfrared or RF remote controller).

The gateway 604, the media processors 606, and media devices 608 canutilize tethered communication technologies (such as coaxial, powerlineor phone line wiring) or can operate over a wireless access protocolsuch as Wireless Fidelity (WiFi), Bluetooth, Zigbee, or other present ornext generation local or personal area wireless network technologies. Byway of these interfaces, unicast communications can also be invokedbetween the media processors 606 and subsystems of the IPTV media systemfor services such as video-on-demand (VoD), browsing an electronicprogramming guide (EPG), or other infrastructure services.

A satellite broadcast television system 629 can be used in the mediasystem of FIG. 6. The satellite broadcast television system can beoverlaid, operably coupled with, or replace the IPTV system as anotherrepresentative embodiment of communication system 600. In thisembodiment, signals transmitted by a satellite 615 that include mediacontent can be received by a satellite dish receiver 631 coupled to thebuilding 602. Modulated signals received by the satellite dish receiver631 can be transferred to the media processors 606 for demodulating,decoding, encoding, and/or distributing broadcast channels to the mediadevices 608. The media processors 606 can be equipped with a broadbandport to an Internet Service Provider (ISP) network 632 to enableinteractive services such as VoD and EPG as described above.

In yet another embodiment, an analog or digital cable broadcastdistribution system such as cable TV system 633 can be overlaid,operably coupled with, or replace the IPTV system and/or the satelliteTV system as another representative embodiment of communication system600. In this embodiment, the cable TV system 633 can also provideInternet, telephony, and interactive media services.

The subject disclosure can apply to other present or next generationover-the-air and/or landline media content services system.

Some of the network elements of the IPTV media system can be coupled toone or more computing devices 630, a portion of which can operate as aweb server for providing web portal services over the ISP network 632 towireline media devices 608 or wireless communication devices 616.

Communication system 600 can also provide for all or a portion of thecomputing devices 630 to function as an image processing server (hereinreferred to as server 630). The server 630 can use computing andcommunication technology to perform function 662, which can includeamong other things, a modified version of Yang's real time filteringalgorithm in which PBFICs are only calculated for certain blocks of theimage based on pixel intensity values for pixels in the block or insurrounding blocks. The media processors 606 and wireless communicationdevices 616 can also be provisioned with software function 662 toperform image filtering such as described in method 500.

In one or more embodiments, the image filtering can be performed in adistributed manner. For example, an image can be partitioned into thegroup of blocks by the server 630 and the server can also performpre-filtering on the image to identify a maximum pixel intensity and aminimum pixel intensity for each block of the group of blocks. Thispre-filtering data can be provided, along with the image, from theserver 630 to a recipient device such as STB 606 or mobile device 616.Based on the pre-filtering data and the image, the recipient device canperform the remaining steps of method 500 including calculating PBFICsfor selective blocks of the image and performing an IIR filtering of theimage based on the calculated PBFICs.

Multiple forms of media services can be offered to media devices overlandline technologies such as those described above. Additionally, mediaservices can be offered to media devices by way of a wireless accessbase station 617 operating according to common wireless access protocolssuch as Global System for Mobile or GSM, Code Division Multiple Accessor CDMA, Time Division Multiple Access or TDMA, Universal MobileTelecommunications or UMTS, World interoperability for Microwave orWiMAX, Software Defined Radio or SDR, Long Term Evolution or LTE, and soon. Other present and next generation wide area wireless access networktechnologies can be used in one or more embodiments of the subjectdisclosure.

FIG. 7 depicts an illustrative embodiment of a communication device 700.Communication device 700 can serve in whole or in part as anillustrative embodiment of the devices depicted in FIG. 6, includingmobile devices, set top boxes, desktop computer, tablets, servers and soforth. Device 700 can utilize bilateral filtering that is selectivelyapplied to blocks of an image to perform image filtering, such as via anIIR filtering methodology. For example, Yang's realtime O(1) bilateralfiltering algorithm can be modified to strategically eliminate some ofthe computations based on blocks of the images having pixels thatsatisfy an intensity threshold. For example, PBFICs can be selectivelycomputed for certain blocks without being computed for other blocks ofthe group of blocks. In this example, the group of blocks can includefirst blocks, first surrounding blocks that are each adjacent to one ofthe first blocks, second blocks, and second surrounding blocks that areeach adjacent to one of the second blocks. PBFICs can be calculated forthe first blocks responsive to determinations that a first pixel withineach of the first blocks has a first intensity level within apre-determined intensity range or responsive to a determination that asecond pixel within the first surrounding blocks has a second intensitylevel within the pre-determined intensity range. Continuing with thisexample, PBFICs would not be calculated for the second blocks wherethere is a determination that pixels within the second blocks haveintensity levels outside of the pre-determined intensity range andresponsive to a determination that pixels within the second surroundingblocks have intensity levels outside of the pre-determined intensityrange. The pre-determined intensity range can be selected based on anumber of factors including, the desired computation time, thecapabilities of device 700, the desired filtering accuracy, the type ofimage being filtered (e.g., an image of the outdoors from a distanceversus a close-up image of a person), and so forth. An infinite impulseresponse filter can be applied by device 700 to the image using thecalculated principle bilateral filtered image components.

To enable these filtering features, communication device 700 cancomprise a wireline and/or wireless transceiver 702 (herein transceiver702), a user interface (UI) 704, a power supply 714, a location receiver716, a motion sensor 718, an orientation sensor 720, and a controller706 for managing operations thereof. The transceiver 702 can supportshort-range or long-range wireless access technologies such asBluetooth, ZigBee, WiFi, DECT, or cellular communication technologies,just to mention a few. Cellular technologies can include, for example,CDMA-1X, UMTS/HSDPA, GSM/GPRS, TDMA/EDGE, EV/DO, WiMAX, SDR, LTE, aswell as other next generation wireless communication technologies asthey arise. The transceiver 702 can also be adapted to supportcircuit-switched wireline access technologies (such as PSTN),packet-switched wireline access technologies (such as TCP/IP, VoIP,etc.), and combinations thereof

The UI 704 can include a depressible or touch-sensitive keypad 708 witha navigation mechanism such as a roller ball, a joystick, a mouse, or anavigation disk for manipulating operations of the communication device700. The keypad 708 can be an integral part of a housing assembly of thecommunication device 700 or an independent device operably coupledthereto by a tethered wireline interface (such as a USB cable) or awireless interface supporting for example Bluetooth. The keypad 708 canrepresent a numeric keypad commonly used by phones, and/or a QWERTYkeypad with alphanumeric keys. The UI 704 can further include a display710 such as monochrome or color LCD (Liquid Crystal Display), OLED(Organic Light Emitting Diode) or other suitable display technology forconveying images to an end user of the communication device 700. In anembodiment where the display 710 is touch-sensitive, a portion or all ofthe keypad 708 can be presented by way of the display 710 withnavigation features.

The display 710 can use touch screen technology to also serve as a userinterface for detecting user input. As a touch screen display, thecommunication device 700 can be adapted to present a user interface withgraphical user interface (GUI) elements that can be selected by a userwith a touch of a finger. The touch screen display 710 can be equippedwith capacitive, resistive or other forms of sensing technology todetect how much surface area of a user's finger has been placed on aportion of the touch screen display. This sensing information can beused to control the manipulation of the GUI elements or other functionsof the user interface. The display 710 can be an integral part of thehousing assembly of the communication device 700 or an independentdevice communicatively coupled thereto by a tethered wireline interface(such as a cable) or a wireless interface.

The UI 704 can also include an audio system 712 that utilizes audiotechnology for conveying low volume audio (such as audio heard inproximity of a human ear) and high volume audio (such as speakerphonefor hands free operation). The audio system 712 can further include amicrophone for receiving audible signals of an end user. The audiosystem 712 can also be used for voice recognition applications. The UI704 can further include an image sensor 713 such as a charged coupleddevice (CCD) camera for capturing still or moving images.

The power supply 714 can utilize common power management technologiessuch as replaceable and rechargeable batteries, supply regulationtechnologies, and/or charging system technologies for supplying energyto the components of the communication device 700 to facilitatelong-range or short-range portable applications. Alternatively, or incombination, the charging system can utilize external power sources suchas DC power supplied over a physical interface such as a USB port orother suitable tethering technologies.

The location receiver 716 can utilize location technology such as aglobal positioning system (GPS) receiver capable of assisted GPS foridentifying a location of the communication device 700 based on signalsgenerated by a constellation of GPS satellites, which can be used forfacilitating location services such as navigation. The motion sensor 718can utilize motion sensing technology such as an accelerometer, agyroscope, or other suitable motion sensing technology to detect motionof the communication device 700 in three-dimensional space. Theorientation sensor 720 can utilize orientation sensing technology suchas a magnetometer to detect the orientation of the communication device700 (north, south, west, and east, as well as combined orientations indegrees, minutes, or other suitable orientation metrics).

The communication device 700 can use the transceiver 702 to alsodetermine a proximity to a cellular, WiFi, Bluetooth, or other wirelessaccess points by sensing techniques such as utilizing a received signalstrength indicator (RSSI) and/or signal time of arrival (TOA) or time offlight (TOF) measurements. The controller 706 can utilize computingtechnologies such as a microprocessor, a digital signal processor (DSP),programmable gate arrays, application specific integrated circuits,and/or a video processor with associated storage memory such as Flash,ROM, RAM, SRAM, DRAM or other storage technologies for executingcomputer instructions, controlling, and processing data supplied by theaforementioned components of the communication device 400.

Other components not shown in FIG. 7 can be used in one or moreembodiments of the subject disclosure. For instance, the communicationdevice 700 can include a reset button (not shown). The reset button canbe used to reset the controller 706 of the communication device 700. Inyet another embodiment, the communication device 700 can also include afactory default setting button positioned, for example, below a smallhole in a housing assembly of the communication device 700 to force thecommunication device 700 to re-establish factory settings. In thisembodiment, a user can use a protruding object such as a pen or paperclip tip to reach into the hole and depress the default setting button.The communication device 700 can also include a slot for adding orremoving an identity module such as a Subscriber Identity Module (SIM)card. SIM cards can be used for identifying subscriber services,executing programs, storing subscriber data, and so forth.

The communication device 700 as described herein can operate with moreor less of the circuit components shown in FIG. 7. These variantembodiments can be used in one or more embodiments of the subjectdisclosure.

The communication device 700 shown in FIG. 7 or portions thereof canserve as a representation of one or more of the devices of system 600 ofFIG. 6. In addition, the controller 706 can be adapted in variousembodiments to perform the function 662.

FIG. 8 depicts an exemplary diagrammatic representation of a machine inthe form of a computer system 800 within which a set of instructions,when executed, may cause the machine to perform any one or more of themethods described above. One or more instances of the machine canoperate, for example, as the server 630, the media processor 606 or themobile device 616 to perform image filtering utilizing PBFICs that areonly selectively calculated for portions of the images (e.g., for afirst set of image blocks but not for a second set of image blocks) inorder to save computational resources. In some embodiments, the machinemay be connected (e.g., using a network 826) to other machines. In anetworked deployment, the machine may operate in the capacity of aserver or a client user machine in server-client user networkenvironment, or as a peer machine in a peer-to-peer (or distributed)network environment.

The machine may comprise a server computer, a client user computer, apersonal computer (PC), a tablet PC, a smart phone, a laptop computer, adesktop computer, a control system, a network router, switch or bridge,or any machine capable of executing a set of instructions (sequential orotherwise) that specify actions to be taken by that machine. It will beunderstood that a communication device of the subject disclosureincludes broadly any electronic device that provides voice, video ordata communication. Further, while a single machine is illustrated, theterm “machine” shall also be taken to include any collection of machinesthat individually or jointly execute a set (or multiple sets) ofinstructions to perform any one or more of the methods discussed herein.

The computer system 800 may include a processor (or controller) 802(e.g., a central processing unit (CPU), a graphics processing unit (GPU,or both), a main memory 804 and a static memory 806, which communicatewith each other via a bus 808. The computer system 800 may furtherinclude a display unit 810 (e.g., a liquid crystal display (LCD), a flatpanel, or a solid state display. The computer system 800 may include aninput device 812 (e.g., a keyboard), a cursor control device 814 (e.g.,a mouse), a disk drive unit 816, a signal generation device 818 (e.g., aspeaker or remote control) and a network interface device 820. Indistributed environments, the embodiments described in the subjectdisclosure can be adapted to utilize multiple display units 810controlled by two or more computer systems 800. In this configuration,presentations described by the subject disclosure may in part be shownin a first of the display units 810, while the remaining portion ispresented in a second of the display units 810.

The disk drive unit 816 may include a tangible computer-readable storagemedium 822 on which is stored one or more sets of instructions (e.g.,software 824) embodying any one or more of the methods or functionsdescribed herein, including those methods illustrated above. Theinstructions 824 may also reside, completely or at least partially,within the main memory 804, the static memory 806, and/or within theprocessor 802 during execution thereof by the computer system 800. Themain memory 804 and the processor 802 also may constitute tangiblecomputer-readable storage media.

Dedicated hardware implementations including, but not limited to,application specific integrated circuits, programmable logic arrays andother hardware devices that can likewise be constructed to implement themethods described herein. Application specific integrated circuits andprogrammable logic array can use downloadable instructions for executingstate machines and/or circuit configurations to implement embodiments ofthe subject disclosure. Applications that may include the apparatus andsystems of various embodiments broadly include a variety of electronicand computer systems. Some embodiments implement functions in two ormore specific interconnected hardware modules or devices with relatedcontrol and data signals communicated between and through the modules,or as portions of an application-specific integrated circuit. Thus, theexample system is applicable to software, firmware, and hardwareimplementations.

In accordance with various embodiments of the subject disclosure, theoperations or methods described herein are intended for operation assoftware programs or instructions running on or executed by a computerprocessor or other computing device, and which may include other formsof instructions manifested as a state machine implemented with logiccomponents in an application specific integrated circuit or fieldprogrammable gate array. Furthermore, software implementations (e.g.,software programs, instructions, etc.) including, but not limited to,distributed processing or component/object distributed processing,parallel processing, or virtual machine processing can also beconstructed to implement the methods described herein. It is furthernoted that a computing device such as a processor, a controller, a statemachine or other suitable device for executing instructions to performoperations or methods may perform such operations directly or indirectlyby way of one or more intermediate devices directed by the computingdevice.

While the tangible computer-readable storage medium 822 is shown in anexample embodiment to be a single medium, the term “tangiblecomputer-readable storage medium” should be taken to include a singlemedium or multiple media (e.g., a centralized or distributed database,and/or associated caches and servers) that store the one or more sets ofinstructions. The term “tangible computer-readable storage medium” shallalso be taken to include any non-transitory medium that is capable ofstoring or encoding a set of instructions for execution by the machineand that cause the machine to perform any one or more of the methods ofthe subject disclosure.

The term “tangible computer-readable storage medium” shall accordinglybe taken to include, but not be limited to: solid-state memories such asa memory card or other package that houses one or more read-only(non-volatile) memories, random access memories, or other re-writable(volatile) memories, a magneto-optical or optical medium such as a diskor tape, or other tangible media which can be used to store information.Accordingly, the disclosure is considered to include any one or more ofa tangible computer-readable storage medium, as listed herein andincluding art-recognized equivalents and successor media, in which thesoftware implementations herein are stored.

Although the present specification describes components and functionsimplemented in the embodiments with reference to particular standardsand protocols, the disclosure is not limited to such standards andprotocols. Each of the standards for Internet and other packet switchednetwork transmission (e.g., TCP/IP, UDP/IP, HTML, HTTP) representexamples of the state of the art. Such standards are from time-to-timesuperseded by faster or more efficient equivalents having essentiallythe same functions. Wireless standards for device detection (e.g.,RFID), short-range communications (e.g., Bluetooth, WiFi, Zigbee), andlong-range communications (e.g., WiMAX, GSM, CDMA, LTE) can be used bycomputer system 800.

The illustrations of embodiments described herein are intended toprovide a general understanding of the structure of various embodiments,and they are not intended to serve as a complete description of all theelements and features of apparatus and systems that might make use ofthe structures described herein. Many other embodiments will be apparentto those of skill in the art upon reviewing the above description. Theexemplary embodiments can include combinations of features and/or stepsfrom multiple embodiments. Other embodiments may be utilized and derivedtherefrom, such that structural and logical substitutions and changesmay be made without departing from the scope of this disclosure. Figuresare also merely representational and may not be drawn to scale. Certainproportions thereof may be exaggerated, while others may be minimized.Accordingly, the specification and drawings are to be regarded in anillustrative rather than a restrictive sense.

Although specific embodiments have been illustrated and describedherein, it should be appreciated that any arrangement calculated toachieve the same purpose may be substituted for the specific embodimentsshown. This disclosure is intended to cover any and all adaptations orvariations of various embodiments. Combinations of the aboveembodiments, and other embodiments not specifically described herein,can be used in the subject disclosure.

The Abstract of the Disclosure is provided with the understanding thatit will not be used to interpret or limit the scope or meaning of theclaims. In addition, in the foregoing Detailed Description, it can beseen that various features are grouped together in a single embodimentfor the purpose of streamlining the disclosure. This method ofdisclosure is not to be interpreted as reflecting an intention that theclaimed embodiments require more features than are expressly recited ineach claim. Rather, as the following claims reflect, inventive subjectmatter lies in less than all features of a single disclosed embodiment.Thus the following claims are hereby incorporated into the DetailedDescription, with each claim standing on its own as a separately claimedsubject matter.

What is claimed is:
 1. A method, comprising: calculating, by aprocessor, principle bilateral filtered image components for firstblocks of an image responsive to determinations that a first pixelwithin each of the first blocks has a first intensity level within apre-determined intensity range or responsive to a determination that asecond pixel within first surrounding blocks of the image has a secondintensity level within the pre-determined intensity range, where thefirst surrounding blocks are each adjacent to one of the first blocks,and wherein second surrounding blocks of the image are each adjacent toone of second blocks of the image; and applying, by the processor, afilter to the image using the principle bilateral filtered imagecomponents.
 2. The method of claim 1, wherein the principle bilateralfiltered image components are not calculated for the second blocksresponsive to a determination that pixels within the second blocks haveintensity levels outside of the pre-determined intensity range.
 3. Themethod of claim 1, wherein the principle bilateral filtered imagecomponents are not calculated for the second blocks responsive to adetermination that pixels within the second surrounding blocks haveintensity levels outside of the pre-determined intensity range.
 4. Themethod of claim 1, comprising performing a pre-filtering technique bydetermining a maximum intensity and a minimum intensity for each blockof a group of blocks including the first and second blocks, wherein thegroup of blocks are of the same size.
 5. The method of claim 1,comprising downsampling the image.
 6. The method of claim 1, whereineach block of the first blocks and the first surrounding blocks has asize of c_(o) by c_(o), wherein c_(o) is equal to a spatial kernelvariance utilized by the filter.
 7. The method of claim 1, wherein theprocessor is a graphics processing unit, wherein each block of the firstblocks has a size of c_(o) by c_(o), and wherein c_(o) is a multiple of16.
 8. A computer-readable storage device comprising computerinstructions which, responsive to being executed by a processor, causethe processor to perform operations comprising: partitioning an imageinto a group of blocks; calculating principle bilateral filtered imagecomponents for a first subset of the group of blocks, wherein theprinciple bilateral filtered image components are not calculated for asecond subset of the group of blocks responsive to: a firstdetermination that pixels within the second subset have intensity levelsoutside of a pre-determined intensity range, a second determination thatpixels within surrounding blocks of the second subset have intensitylevels outside of the pre-determined intensity range, or a combinationthereof; and applying a filter to the image using the principlebilateral filtered image components.
 9. The computer-readable storagedevice of claim 8, wherein a selection of the first subset of the groupof blocks is based on determinations that a first pixel within eachblock of the first subset has a first intensity level within apre-determined intensity range.
 10. The computer-readable storage deviceof claim 8, wherein a selection of the first subset of the group ofblocks is based on a determination that a second pixel within asurrounding block of each block of the first subset has a secondintensity level within the pre-determined intensity range.
 11. Thecomputer-readable storage device of claim 8, wherein each block of thegroup of blocks has a size of c_(o) by c_(o), wherein c_(o) is equal toa spatial kernel variance utilized by the filter.
 12. Thecomputer-readable storage device of claim 8, wherein the operationsfurther comprise downsampling the image.
 13. The computer-readablestorage device of claim 8, wherein the filter utilizes a spatial kernelvariance between 4 to
 40. 14. The computer-readable storage device ofclaim 8, wherein the filter utilizes a range kernel variance between0.04 to 0.3.
 15. The computer-readable storage device of claim 8,wherein the processor is a graphics processing unit, wherein each blockof the group of blocks has a size of c_(o) by c_(o), and wherein c_(o)is a multiple of
 16. 16. A device comprising: a memory that storescomputer instructions; and a processor coupled with the memory, whereinthe processor, responsive to executing the computer instructions,performs operations comprising: calculating principle bilateral filteredimage components for a first subset of a group of blocks of an image,wherein the principle bilateral filtered image components are notcalculated for a second subset of the group of blocks responsive to: afirst determination that pixels within the second subset have intensitylevels outside of a pre-determined intensity range, a seconddetermination that pixels within surrounding blocks of the second subsethave intensity levels outside of the pre-determined intensity range, ora combination thereof; and applying a filter to the image using theprinciple bilateral filtered image components.
 17. The device of claim16, wherein a selection of the first subset of the group of blocks isbased on determinations that a first pixel within each block of thefirst subset has a first intensity level within a pre-determinedintensity range.
 18. The device of claim 16, wherein a selection of thefirst subset of the group of blocks is based on a determination that asecond pixel within a surrounding block of each block of the firstsubset has a second intensity level within the pre-determined intensityrange.
 19. The device of claim 16, wherein each block of the group ofblocks has a size of c_(o) by c_(o), wherein c_(o) is equal to a spatialkernel variance utilized by the filter.
 20. The device of claim 16,wherein the operations further comprise downsampling the image.